1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
Trench isolation has widely been used in the field of semiconductor devices. Trench isolation is utilized for isolation of a MOS (Metal Oxide Semiconductor) transistor, bipolar transistor, and the like.
One of trench isolation techniques is to cover the opening of a trench with a cap layer made of an insulator and form an airtight space in the trench. This technique is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2-119238. According to this technique, the trench is filled with gas whose relative dielectric constant is low. This technique is effective particularly in a high voltage device.
However, the present inventors have found that a cap layer formed by the prior art is readily destructed in a heat treatment such as activation annealing.